1. Field of the Invention
The present invention relates to a deflection yoke apparatus having a cancellation coil for canceling a leakage magnetic field leaking from the deflection yoke.
2. Description of the Related Art
Studies and reports have recently been made of the adverse influence on human bodies (especially in the case of pregnant women) caused by leakage magnetic fields leaking from the deflection yoke of the cathode-ray tube of a television receiver, a display or the like. Means, therefore, have become adopted to prevent the adverse influence of leakage magnetic fields leaking from the deflection yoke of such electronic equipment.
FIG. 1 illustrates a deflection yoke apparatus having a means for such prevention. The apparatus has a deflection yoke 1, and a leakage field cancellation coil 4 provided on the top side, the bottom side, or both of a large-diameter portion 3 of the head of a bobbin 2 of the yoke 1. The leakage field cancellation coil 4 comprises a ring-shaped coil winding (not shown) accommodated in a box-shaped coil case 5. When the coil case 5 accommodating the coil winding is covered with a coil cover 7 having a leg 6, the coil case 5 and the coil cover 7 are integrated with each other. An arm-shaped joint 10 having a bent base portion is mounted on an end face 8 of the large-diameter portion 3 (the face 8 being on the same side as the neck). When pawls 11 of the joint 10 are brought into engagement with engagement bores 12 in the leg 6 of the coil cover 7, the leakage magnetic field cancellation coil 4 is mounted onto the joint 10, hence, onto the deflection yoke 1.
With the deflection yoke apparatus having the leakage magnetic field cancellation coil 4, a leakage magnetic field leaking from the horizontal or vertical deflection coil(s) of the deflection yoke 1 is offset by a cancellation magnetic field generated by the leakage magnetic field cancellation coil 4. In this way, the leakage magnetic field leaking to the outside of the cathode-ray tube is diminished to thereby prevent adverse influence on human bodies.
However, the conventional deflection yoke apparatus has the following drawback. The provision of the leakage magnetic field cancellation coil 4 necessitates preparing the coil case 5 and the coil cover 7, which are separate members, as different formed products. This formation inevitably requires high material costs. In addition, the leakage magnetic field cancellation coil 4 inevitably forms a large assembly when the coil case 5 and the coil cover 7 are integrated together.
Another drawback comes from the manner in which the leakage magnetic field cancellation coil 4 is mounted onto the deflection yoke 1, that is, the mounting of the cancellation coil 4 being accomplished through the intervention of the joint 10. This means an increase in the number of component parts. In addition, the operation of assembling the leakage magnetic field cancellation coil 4 assembly, and mounting the cancellation coil 4 onto the deflection yoke 1 is complicated, and has poor operational efficiency.